To extend studies concerning serum and spinal fluid complement components in patients with central nervous system manifestations of S.L.E. In particular, to continue to study the correlation of serum and CSF complement analyses and clinical course in order to supplement available data. This will include an analysis of participation of the alternate pathway of complement activation by measurement of serum levels of the C3 proactivator by radial immunodiffusion. To investigate abnormalities of spinal fluid complement in neuropsychiatric disorders other than S.L.E. Assays of complement components and an attempt to demonstrate reaction products or activated components will be carried out. To extend previous studies from our laboratory concerning the in vivo metabolism of C3 in human disorders. Specific aims will be to study the correlation of the characteristics of complement metabolism (catabolic rate, synthetic rate, components activated--i.e., C3 and/or C4) with clinical parameters, and to study the possibility of using C3 and C4 catabolic rates as a means of documenting clinical activity of the disease at a time that serum concentrations of complement components are normal. To study the quantitative immunology of red cell sensitization with complement components in acquired hemolytic anemias in order to correlate such quantitation with clinical findings and with serologic reactions (direct Coombs' test titration scores and serum antibody titers, etc.) in addition to further clarifying the role of complement in immune red cell destruction. Bibliographic references: Drug-Induced Immune Hemolytic Anemia. G. Garratty and L.D. Petz. Amer J Med 58:398, 1975; Phagocytes and C4 in Paraproteinaemia. L. E. Spitler, P. Spath, L. Petz, N. Cooper, and H. H. Fudenberg. Brit. J. Haemat. 29:279, 1975.